结构异性煤层顺层钻孔方位对有效抽采半径的影响

为了提高煤层顺层钻孔瓦斯抽采效率，有效抽采半径的确定是关键。基于各向异性煤层瓦斯渗透率测试结果，建立了煤层瓦斯各向渗透异性的气-固耦合渗流模型，数值模拟了不同钻孔方位时瓦斯抽采有效半径的时变规律，分析了钻孔方位对抽采效果的影响。研究结果表明：煤层面割理和端割理方向渗透率均大于垂直层理方向渗透率；钻孔有效抽采半径随抽采时间增加呈幂指数增大；煤层有效抽采区域是以抽采钻孔为中心，最大抽采距离(平行层理方向)为长轴，最小抽采距离(垂直层理方向)为短轴的椭圆。平行层理沿端割理方向抽采孔的瓦斯抽采效果优于平行层理沿面割理方向的抽采孔。

Influence of effective drainage radius by borehole orientation along seam with anisotropic permeability

In order to improve gas drainage efficiency along seam,the key is to determine borehole orientation and effective drainage radius.Based on the gas permeability test results of anisotropic coal seam,the gas-solid coupling seepage model in gas anisotropic permeability coal seam is established to numerically simulate the time variation laws of effective drainage radii of different borehole orientations,and to analyze the influence of drainage effect by borehole orientation.The results show that the gas permeabilities at the directions of face cleat and butt cleat are about 2.6 times and 1.5 times respectively larger than that on the direction vertical to the bedding plane.In any direction,effective dranage radii increases with gas drainage time increasing,but increasing rates gradually decrease,which the relationship of effective drainage radii and gas drainage time can be expressed by power exponent.Effective drainage area is an ellipse under any gas drainage time in gas anisotropic permeability coal seam,and the ellipse center is drainage borehole,its long axis and short axis are maximum drainage distance (parallel bedding direction) and minimum extraction distance (perpendicular to the direction of the bedding) respectively.The gas drainage effect of drainage hole parallel bedding along butt cleat derection (perpendicular to face cleat) is better than that of drainage hole parallel bedding along face cleat derection (perpendicular to butt cleat).This research provides the basis for the selection of borehole orientation and reasonable arrangement of boreholes,which has significance to improve gas drainage efficiency and ensure mine safe production.